1. Field of the Invention
The present invention relates to a printer and, more particularly, to a multi-beam scanning apparatus for simultaneously deflecting and scanning at least two beams emitted from optical sources to form an electrostatic latent image on a photoreceptor.
2. Description of the Related Art
A general beam scanning apparatus adopted in a printer charges a photoreceptor by a main scan using a beam deflector and a sub-scan using transfer or rotation of the photoreceptor.
FIG. 1 shows the optical arrangement of a conventional beam scanning apparatus which includes an optical source 1 for emitting a beam of light, a beam deflector 4 for deflecting the beam emitted from the optical source 1, and an f-theta (f-.theta.) lens 7 for correcting the error of light deflected by the beam deflector 4.
Also, a focusing lens 3 is installed between the optical source 1 and the beam deflector 4 to focus a divergent beam emitted from the optical source 1. The beam deflected by the beam deflector 4 is reflected by a reflective mirror 8, and the reflected beam proceeds toward a photosensitive drum (not shown).
The beam deflector 4 includes a motor 5 and a rotating polygonal mirror 6 which is rotated by the motor 5. The beam emitted from the optical source 1 is deflected according to the angle formed between itself and a reflective facet of the rotating polygonal mirror 6. Accordingly, the beam deflection is sensitive to wobble generated when the rotating polygonal mirror 6 is rotated.
In the case of a color printer, a separate beam scanning apparatus corresponding to each specific color must be installed, thus the color printer is complicated and large.